I will note that other occupancy codes, like property maintenance, often have a requirement for light and fresh air, I suspect this is why we see hotel windows that are "just operable" enough for air? It is likely that a new dormitory meeting NFPA 101, chapter 28 and utilizing a sprinkler system would not be required to have a secondary means of escape (very often minimum sized operable windows). I know our Code Office will not permit sleeping rooms without fresh air but I'm not clear which code they cite?

I would say you may on the right track here. The additional heating and cooling loads by allowing the windows to remain open may over ride the capacity of many HVAC system designs. I would say the building codes would permit mechanical ventilation in lieu of windows to provide the required fresh air ventilation for each dorm room and other occupied spaces. I looked through the occupancy requirements for New Hotels and Dormitories in the 2018 NFPA 101 and did not see any requirements for open-able windows for secondary escape and venting smoke for fire safety. I would also say the window glazing must be friable to avoid smoke control system requirements of the building and life safety codes.

Of course, I can not speculation what the local building codes and regulations might require.

IF OHSA require fresh air option 3 or 4 in code or intake and outlet both on outside wall bottom and top, have done couple with small fans with motion sensors, when no openable windows in small dorm rooms.

I am Proff Fire Engineer always concerned about people safety. Get local fire engineer and he will do on site assessment of practical options. Difficult to comment without 3d view of situation number of storeys, escape distance population size and configurations etc. Therefore stay with code until professional could apply judgement / rational design to deviate.

In accordance with Section 28.2.1.2 of NFPA 101 (2018 ed.) for new dormitories and Section 29.2.1.2 of NFPA 101 for existing dormitories, means of escape within the guest rooms or guest suite must comply with 24.2 for one- and two-family dwellings. Section 24.2.2 requires a secondary means of escape from every living area and sleeping room, unless the building is protected throughout by an approved automatic sprinkler system.

In most cases, windows are the secondary means of escape, so unless the building is fully sprinklered, then the windows are probably required to be operable. I would recommend, though, that you consult with the local AHJ for a proper determination, as there may be other allowances, or it could be that NFPA 101 is not adopted in the jurisdiction in which the dormitory is located.

There is always more to add from the discovery of facts that change the parameters.

Its just human nature to look for an individual code section of NFPA 101 to satisfy prejudiced experiences with building and life safety codes.

Compliance with the provisions of Section 24.2 Means of Escape Requirements as referenced by Section 28.2.1.2 of the 2018 NFPA 101 New Hotel and Dormitory Occupancies is conditional that a dorm room has two rooms more. Most dorm rooms I have been in has one room.

Plus the fact, Section 28.3.5.1 the building must be protected throughout by an approved supervised automatic sprinkler system in accordance with 28.3.5.3. Section 28.3.5.3 permits dormitory occupancies up to and including four stories in height in a building not exceeding 60 ft in height above grade plans are permitted to have a NFPA 13R system.

Applying the requirements of Section 24.2.2.1.2, the secondary means of escape was not required where the dorm room is protected throughout by an approved automatic sprinkler system in accordance with 24.3.5. The NFPA 13 or NFPA 13R sprinkler system, to me, would be acceptable for compliance to Section 24.3.5.

If fact, the windows used for the secondary means of escape are limited to those that are within 20 ft of the finished ground level in accordance with 24.2.2.2.3 (1). This means to me that dorm rooms with windows above this height must comply with Chapter 7 Means of Egress.

With some certainty, in terms of NFPA 101, I would say in a building protected by an approved supervised automatic sprinkler system and in compliance with Chapter 7 Means of Egress, the dorm rooms would not need open-able windows for the means of escape.

I can not speculate what the local building codes and regulations are for open-able windows in dorm rooms.